Can You Change Cura Units from Millimeters (mm) to Inches (in)?

It’s undeniable that Cura is one of the most feature-packed and quickly evolving slicers available for 3D printing right now, making it possible to customize everything related to the printing process through its user-friendly interface with a few clicks of buttons in most cases.

On the other hand, the features that the 3D printing community looks for in slicer software grow just as rapidly as Cura evolves, which is not surprising as the same principle applies to almost any software and especially the ones on the newer side, as there is always something new that can be added.

Today, we will be finding out whether Cura offers the particular feature of switching its default units from millimeters, which is a unit that belongs to the metric system, to inches, which is the measurement unit used in the imperial system, and the standard in countries such as the United States.

So, is it possible to change the default units of Cura to inches from millimeters?

Unfortunately, as millimeters are widely accepted to be the standard unit of measurement for length in the 3D printing world, it’s not possible to change the default units of Cura from millimeters to inches, which practically is how it works for all 3D printing-related software.

Next up, we will examine the topic of changing Cura units from millimeters to inches in more detail, find out how to convert between millimeters and inches quickly, go through the process of specifying measurement units for an imported STL file, and finally, take a quick look at the process of switching from millimeters to inches directly in Marlin firmware.

Can You Change Cura Units from Millimeters (mm) to Inches (in)?

There is no denying that the units in Cura being in millimeters by default can be problematic for users from countries such as the United States, where the imperial system is used, as understanding metric units won’t be straightforward in such a case.

As it stands, there is no Cura feature or community-made plugin that allows the user to switch between millimeters and inches, making millimeters, which is the unit accepted to be the standard in 3D printing, the only length unit that you can use in Cura.

At the time of writing, it doesn’t seem like there are any plans to include such an option either, as the information we have gathered through Ultimaker forums points towards the Ultimaker team believing that the feature is unnecessary due to reasons such as the metric system being the scientific system that should be used and that adding such a feature would make it harder to maintain Cura from a development perspective.

As a result, the only way to convert between millimeters and inches is to do it manually whenever necessary and input the millimetric value you have calculated into Cura.

How to Quickly Convert Between Millimeters and Inches?

Performing the calculations to switch back and forth between millimeters and inches is a pretty straightforward process once you know the formula, meaning that you can quickly find the millimeter values to input into Cura without a lot of trouble.

To convert between millimeters and inches quickly, the only piece of information you need to know is that 1 inch equals 25.4 millimeters, and with this information, you can use simple mathematics to convert between millimeters and inches whenever necessary.

So, by multiplying a value in inches by 25.4, you can find its millimetric equivalent, and by dividing a value in millimeters by 25.4, you can calculate its inch equivalent.

If you wish, you can also bring this process further by exporting your Cura profiles into spreadsheets and using formulas that will automatically convert all the millimetric units into inches to see conversions for all parameters at once and in real-time whenever you make modifications.

How to Specify Units for an Imported STL File in Cura?

As the STL file does not carry information about the units of the model’s measurements, Cura will automatically assume that the STL file you have imported is designed in millimeters unless you take an extra step to specify the units Cura should use for creating the meshes.

We highly recommend downloading and installing the Mesh Tools plugin for Cura to be able to specify units for an imported STL file in Cura, as this functionality does not exist in Cura by default.

After installing the Mesh Tools plugin, you can follow the steps below to get Mesh Tools to make the necessary conversion:

  1. Click the Extensions option on the top menu of Cura.
  2. Hover over the Mesh Tools option in the dropdown.
  3. Click the Mesh Tools Settings option.
  4. Choose the unit that you designed your STL file with in mind from the dropdown menu, and close the dialog.

The next time you import a model into Cura, Mesh Tools will automatically perform the necessary calculations assuming that the model you have imported is designed with the unit you have chosen through the dropdown, and resize the model accordingly.

How to Switch Units Between Millimeters and Inches in Marlin Firmware?

While it’s not possible in Cura, there is a way to get your 3D printer to accept the G-code parameters in imperial units if you’re running Marlin firmware, which can come in handy if you frequently issue G-code commands that contain measurements and are familiar with the imperial system.

Marlin firmware offers two separate G-code commands for switching between millimeters and inches, which are G20 (Inch Units) for converting to inches and G21 (Millimeter Units) for converting to millimeters. 

Executing the G-code command that corresponds to the unit you wish to switch to will prompt Marlin to conduct the switch automatically, and everything where the currently active units (millimeters by defaults) are used, such as positions and offsets, will be converted.

As it’s entirely possible to switch back and forth without any problems at all times, you can feel free to convert the units to the one you need whenever you deem necessary by using the G20 and G21 G-codes. 

Wrapping Up

Even though the millimeter is accepted to be the standard measurement unit in the 3D printing world, many 3D printing enthusiasts are more familiar with the imperial system due to it being the standard in their region, which can make it challenging to think of measurements in terms of millimeters.

To quickly recap, the unfortunate reality is that it’s currently (and for the foreseeable future) not possible to switch from the default length unit of millimeters to inches in Cura, as millimeters are the universally accepted length unit in the world of 3D printing as it stands.

While this can be a slight inconvenience for those who are more familiar with the imperial system at first, converting between millimeters and inches, especially when you get used to it after 3D printing for a while, is something you can quickly and easily calculate in most cases.

Happy printing!